Scales for Blues Playing

Part I, The Blues

Why the blues? Well, the blues is a great way to practice soloing - there are (usually) only three major chords, so you can keep track of what's happening and what's coming up pretty easily. I'll inject a little bit of music theory during this lesson, but this isn't meant to be a music theory study - there are better sources of that information on the internet. What I intend to show here is only a framework for visualizing the scales. Once you understand it, try to forget about scale patterns and allow your ear to guide you instead. If you don't understand the terminology, ask here or on a forum or just search the web.
Not interested in playing the blues? This lesson is still for you. Once you can grasp how to organize your changing scales into overlapping patterns, you can use this technique with other types of music as well. Note that this lesson uses a blues pattern that follows three dominant chords (i.e. b7th chords), so the patterns presented below are mainly of interest to blues players. For other styles, you may do better referring to Modes for Dummies.

Part II, Root Note Chasing

People often associate one pentatonic and blues scales as the starting point for blues soloing. I did that for years but was often struck that:
a) the notes in the pentatonic scale didn't always sound right for the different chords that were being played
b) when I analyzed my favorite blues solos, musicians were often playing "other" notes and they always sounded better than me
To remedy this, I tried to better match my solo notes to the chord that was being played. I started chasing the root note. And to do this, I would shift my favorite scale patterns around on the guitar neck to match whatever the root note of the current chord was. While this is one way to approach it, it didn't always sound right, and doing huge jumps around on the fretboard required a lot of speed and accuracy and a bit of mental dexterity as well. If you get off track with the chords in the song, you can get lost pretty quickly. It also makes transitioning to just playing by ear more difficult.
For example, let's assume we're doing basic 12-bar blues in A-major. The chords could all be played as 7th's (or with a blues shuffle pattern). They would then be A7, D7, and E7.
During the A7 chord, you could start with the A-major blues scale at the 5th fret (for now, I'm assuming the root note is on the low E string, but that's not necessary).

- R - 2 b3
- 5 - 6
2 b3 3
6 - - R
3 - - 5
- R - 2 b3

In this case, the R is the root note (A), 2 is the second note (B), and so on. That is, it refers to name of the notes position (it is not a fret number). You might prefer to think of blues scale in A-major with the notes going down to the left, but we'll use this pattern for now.
In blues, you will often bend through or from the b3 note, or use it as a passing note. In addition, we often play or bend the b7th note up a whole step. Recall the normal blues shuffle pattern is alternating between the 5, 6 and b7 notes, so we're hearing these notes often during the song.
If you refer to my Modes for Dummies lesson, you'll recognize this as most of the notes that outline a G7 chord when in the key of C, with the addition of the blue b3 note.
Here is the same pattern, but showing examples of common string bends.

- x - x b
- x - x B
x b x
x - - x
x - - x
- R - x b

In this case, I'm using "b" to mean a half-step bend, and "B" to mean a full-step bend. You instead of doing a half-step bend from the b3rd, you can also do a full step bend from the 2nd.
Now if we chase the root note on the low e string, we would use the above pattern with R at the 5th fret during the A7 chord, at the 10th fret during the D7 chord, and at the 12th fret during the E7 chord. That might get tiring.

Part III, Single Position Playing

Instead of moving the same pattern up and down the neck, we can instead approach this by moving all three blues scales associated with a 3 chord blues song into one fretboard position, and modify which notes to keep and discard while we're playing. We can also find a lot of "safe" notes to try when we get lost (! ).
There are two possible ways of folding these scales together, with the root notes on the top two strings. I'll show you one and you can work out the other if you're interested.

- - - -
- - - -
- - -
- - - -
- IV - V
- I - -

You could also arrange the chord root notes like the following. The I is on the A-string and the other chord's roots on the E-string. Below the I is at the 12th fret (A note on the A-string). However, I'm going to focus on the above pattern for the rest of this lesson.

- - - -
- - - -
- - -
- - - -
- - - I
- IV - V

In both of the above, "I" is showing the root note of the Tonic (main) chord, A7 in this case, IV is root note of the Subdominant (D7) chord, and V is the root note of Dominant (E7) chord (sorry, need to use some music theory names here - main things is just recognize the L-shaped pattern of the root notes of the three main chords).
Now let's look at combining the scales into one position. Following are the three blues scales for the I, IV, and V chords shown next to each other, all arranged around the 5th fret.
A-major blues (R=5th fret on low E-string):

- R - 2 b3
- 5 - 6
2 b3 3
6 - - R
3 - - 5
- R - 2 b3

D-major blues (R=5th fret on A-string):

- 5 - 6
- 2 b3 3
6 - - R
3 - - 5
- R - 2 b3
- 5 - 6 -

E-major blues (R=7th fret on A-string):

3 - - 5
- R - 2 b3
5 - 6 -
2 b3 3
6 - - R
3 - - 5

You can see that changing from the A-major blues to the D-major blues does not require that much change, nor does changing from A-major blues to E-major blues. Note that you can also just play the D-major blues pattern up two frets when the E7 rolls around (but I'm trying to emphasize the scales in one fretboard position, so forget I said that).
Here are the same scale patterns, but written out with the common string bends. Note where the overlaps occur between patterns and you'll realize why some of these sounded good while you were playing, regardless of what chord was being played.
A-major blues (R=5th fret on low E-string):

- x - x b
- x - x B
x b x
x - - x
x - - x
- R - x b

D-major blues (R=5th fret on A-string):

- x - x
- x b x B
x - - B
x - - x
- R - x b
- x - x

E-major blues (R=7th fret on A-string):

x - - x
- x - - b
x - x B
x b x
x - - R
x - - x

Here I'm using "b" to mean a half step bend, and "B" to mean a full step bend.
You may have other favorite notes to bend, but I offer a few just to show the places that overlap between the scales. I have other notes that I like to throw in too, but this can give you a starting point for seeing how the notes overlap.

Part IV, Turn Arounds

This section is just additional information on blues turnarounds. Many blues songs use a little turnaround with half-step shifts down. I realized that if you look at these as moving 7th chords, you can pick-and-choose different notes from these so you don't always use the same turnaround.
So here is my collection of favorite turnarounds (played as triplet notes in these examples). All are shown for A-major blues - shift as required.

You can use use triplet single notes as shown, finger pluck chords, or strum. If you have any favorite turnarounds, please post them...

Part V, Conclusion

This lesson provided visual aids to approach overlaying scale patterns for a simple 3-chord song. Use the ideas presented to produce your own strategy. Expand the examples show to include root notes on other strings. Finally, forget the scales and patterns and just play what sounds best.